HANNOVER, Germany (AP) -- President Barack Obama opened a two-day visit to Germany on Sunday hoping to counter deep public skepticism about a trans-Atlantic trade deal with Europe as the continent grapples with economic challenges, terrorism and other pressing issues.
Chancellor Angela Merkel warmly greeted Obama on what is likely his final visit as president to Germany, rolling out a red carpet at Hannover's sprawling Herrenhausen Palace, a rebuilt version of the former summer royal residence destroyed in World War II.
After reviewing German troops in a palace garden, they climbed a spiral staircase and stepped inside for private talks.
Although the Trans-Atlantic Trade and Investment Partnership was the primary focus of Obama's visit, other issues couldn't be ignored, chiefly efforts to counter the Islamic State group, improve cooperation on counterterrorism, and encourage countries to share law enforcement information. IS has claimed responsibility for attacks in Brussels last month that killed more than 30 people.
Obama also wants to give a public show of support for Merkel's "courageous" handling of the migrant issue. Her decision to allow the resettlement in her country of thousands fleeing violence in Syria and other Mideast conflict zones created an angry domestic backlash. Merkel recently helped European countries reach a deal with Turkey to ease the flow, but she and the other leaders are now under pressure to revisit it.
Obama has a tough sell to make for the trade deal known as TTIP, particularly in Germany. He was joining Merkel later Sunday to open the Hannover Messe, the world's largest industrial technology trade fair, and promote the agreement.
Thousands of people took to the streets in protest in Hannover on Saturday, the day before Obama arrived. Some carried placards that said "Yes We Can — Stop TTIP!" It was a riff on Obama's 2008 presidential campaign slogan.
In November, more than 100,000 people in Berlin protested against the proposed pact.
Proponents say the deal would boost business at a time of global economic uncertainty. Critics fear the erosion of consumer protections and environmental standards.
Negotiators in Washington and Europe are trying to finalize key parts of the deal before the end of the year, after which Obama's successor and election campaigns in major European countries could further complicate the already difficult negotiations.
Obama said it was important to conclude negotiations even though ratification would be unlikely before he leaves office. "But if we have that deal, then the next president can pick that up rapidly and get that done," he told the BBC in an interview broadcast Sunday.
It's not certain that the next president would pick up where Obama leaves off on the trade deal. The pact has not been a top issue in the campaign to choose Obama's successor, but both leading candidates — Democrat Hillary Clinton and Republican Donald Trump — oppose a pending Asia-Pacific trade pact for its potential impact on American jobs and wages.
In London on Saturday, Obama acknowledged the tough work that is needed to complete the negotiations with Europe.
Despite "enormous amounts of trade" between the U.S. and Europe, "there's still barriers that exist that prevent businesses and individuals that are providing services to each other to be able to do so seamlessly," Obama said.
He said trade negotiations are tough because each country fights for its own interests.
"The main thing between the United States and Europe is trying to just break down some of the regulatory differences that make it difficult to do business back and forth," he said.
Obama has worked with Merkel throughout his two terms, in good times and bad, and he wanted to show political solidarity with her, particularly on the migrant issue. Her approach to the crisis "has been courageous," he said.
Merkel and top European officials traveled near the Turkish border on Saturday to promote the EU-Turkey deal on migrants.
"She's demonstrated real political and moral leadership," Obama told the German daily Bild in an interview published Saturday. "The politics around refugees and immigration is hard in any country, but I believe the best leaders are willing to take on the toughest issues, especially when it's not easy."
Obama was likely to contrast Merkel with the Republican presidential candidates at home who want to block Muslims from entering the U.S.
On Monday, Obama was joining Merkel to tour the trade show and giving a speech on challenges facing the U.S. and Europe.
Merkel also used the occasion of Obama's visit to invite the leaders of France, Britain and Italy to Hannover for a meeting Monday to discuss Syria, Libya, IS, migration and other issues.